Friday, 11 November 2011

Calunium is an Arduino clone based on the ATmega1284 microcontroller. Initially a strip board design was created to test the concept. Following the success of the strip board version I decided to create a PCB version. Initially I hoped to include Wifi networking, an SD card and a real-time clock. It soon became apparent that including this many peripherals was not possible with the desired footprint using the free version of Cadsoft Eagle. The final version includes a real-time clock. Wifi networking (using the Roving Networks XV Wifi module) and storage using an SD card is provided by a shield designed specifically for Calunium. The RN-XV/SD shield will be described in a future blog post. The pin mapping of the PCB differs slightly from the strip board version; the Arduino software takes care of the differences provided the correct board type is selected.

Features

Shield-compatible with Arduino Uno, with extra I/O laid out to be compatible with Arduino Mega pins. Pin mapping is chosen for maximum compatibility with Uno.

I2C (SDA/SCL) mapped to standard location as used by Arduino Mega but jumpers can be used to replace A4/A5 with SDA/SCL signals for compatibility with Arduino Uno.

Second UART (D1,D2) signals also mapped to corresponding location on Arduino Mega (TX1,RX1).

ISP header in standard location, allowing the Arduino ethernet/SD shield to be used.

D13 LED connected via FET to avoid loading D13.

Direct USB interface using V-USB, for firmware updates without requiring FTDI cable. Can be disabled by removing jumpers. Not yet tested.

Real-time clock (DS1307). Output square wave can be routed to D6 (INT2) or D15 (TOSC1, for input to timer/counter 2). Use either CR2032 or CR1220 battery depending upon battery holder fitted.

Power from USB or FTDI connector.

Switches, jumpers, connectors and USB socket outside of the standard Arduino shield footprint so they do not interfere with shields and are accessible when shields are fitted.

Auxiliary power connector; connect your own voltage regulator or boost converter. 5V from USB (FTDI and/or USB connector) and 3V from RTC battery also available on the connector. 3.3V operation is also possible.